Interpretive Summary: Campylobacter jejuni is a common causative agent of bacterial gastroenteritis throughout the world. The development of improved molecular methods for tracing the sources of this ubiquitous pathogen is an essential component in controlling human illness caused by C. jejuni. In this study, a whole genome DNA microarray typing tool called comparative genome indexing (CGI) was used in conjunction with statistical methods to identify the most informative genes useful for discriminating C. jejuni isolates and for developing a simplified microarray typing method. A group of 95 geographically diverse cattle, chicken and human C. jejuni isolates were selected for the study. Statistical analyses of the whole genome data from each isolate identified 142 significantly informative genes for use in differentiating the isolates. Our results indicate this group of genes will be useful in developing a reduced gene set for CGI as a molecular subtyping tool for C. jejuni and as a means of further understanding the epidemiology and population genetics of this ubiquitous pathogen.

Technical Abstract:
Campylobacter is a leading cause of food borne illness in humans and improving our understanding of the epidemiology of this organism is essential. The objective of this study was to identify the genes that were most significant for discriminating isolates of C. jejuni by analyzing whole genome DNA microarrays. Statistical analyses of whole genome data from 95 geographically diverse cattle, chicken and human C. jejuni isolates identified a total of 142 most significant variable genes. Of this total, 125 (88%) belonged to genomic prophage and hypervariable regions. The significance of genomic prophage and hypervaiable regions in determining C. jejuni isolate genomic diversity is emphasized by these results. These genes should prove useful in the development of genotyping systems for C. jejuni as well as a means to further our understanding of the epidemiology and population genetics of this major food-borne pathogen.